"Interactions between drugs, and other substances, can put older people at a real risk of everything from low blood sugar to kidney damage and accidents caused by sleepiness," said Dr. Preeti Malani, who directed the nationwide poll.

"At the very least, a drug interaction could keep their medicine from absorbing properly," said Malani, a professor at the University of Michigan Medical School.

The poll was conducted by the university's Institute for Healthcare Policy and Innovation. It was sponsored by AARP and Michigan Medicine, the university's academic medical center.

Malani's team questioned nearly 1,700 adults ages 50 to 80. About 1 in 3 who take at least one prescription drug had talked to a health care professional about possible drug interactions in the past two years, the results showed.

Even among those taking six or more medicines, fewer than half had talked with a health care professional about possible drug interactions.

"It's important for anyone who takes medications to talk with a health care professional about these possibilities," Malani said in a university news release.

Use of multiple pharmacies and doctors may play a role in this lack of communication, the poll findings suggest. One in 5 respondents said they had used more than one pharmacy in the past two years, including retail and mail-order. And 3 in 5 see more than one doctor for their care.

More than 60 percent of respondents said they believe their doctor and pharmacist are equally responsible for identifying and talking about possible drug interactions. But only 36 percent said their pharmacist knows about all the medications they're taking when they fill a prescription.

And while 90 percent of respondents said they were confident that they knew how to avoid drug interactions, only 21 percent were very confident.

Alison Bryant is senior vice president of research for AARP. "Even with trackers and systems in place, patients need to be open with their providers and tell them all the medications and supplements they're taking, including herbal remedies," she said.

"It's especially important for older adults to be vigilant about this because they tend to take multiple medications," Bryant noted.